Hitherto, a gas barrier film composed of a resin substrate on which a thin layer of metal oxide is formed is widely used for packaging a product requiring to be insulated from gas such as moisture and oxygen or packaging for preventing deterioration of foods, industrial products and medicines.
Moreover, such the barrier material is used for liquid crystal displaying elements, solar cells and electroluminescence (EL) substrate other than the packaging material. Recently, the transparent substrate which is progressively applied to the liquid crystal elements and the organic EL elements is required to be light weight and large size and further required higher requirements such as long durability, high freeness in form and ability for displaying on curved face. Therefore, the use of film materials such as transparent plastics begins as the transparent substrate in stead of a glass substrate which is heavy, easily broken and difficulty made in a form of large area plate.
However, there is a problem such as that the transparent plastic film substrate is inferior to glass in the ability of gas barrier. When a material inferior in the gas barrier ability is used, moisture or air penetrates so as to deteriorate the liquid crystals in the liquid crystal cell and cause displaying defects and lowering in the displaying quality.
It has been known for solving such the problem to use a gas barrier film material which is prepared by forming a thin layer of metal oxide on a film substrate. As the gas barrier film to be used for the packaging material and the liquid crystal display, a plastic film is known, on which silicon oxide (Patent Document 1) or aluminum oxide (Patent Document 2) is vapor deposited. Both of them have a moisture barrier ability of about 1 g/m2/day.
Recently, the requirement to the gas barrier ability of the film substrate is raised to a level of about 0.1 g/m2/day accompanied with the development of organic EL, large size liquid crystal display and high definition display.
Furthermore, the development of the organic EL display and the high definition color display is rapidly progressed. Consequently, a multilayered material is recently desired, which has higher gas barrier ability, particularly less than 0.1 g/m2/day, while maintaining transparency capable of applying in such the field.
Corresponding to the above requirements, thin layer forming methods for producing a barrier resin substrate having a structure composed of alternatively piled polymer layers and gas barrier layers, for example, cf. Patent Documents 3 and 4. However, the thin layer forming methods proposed there have problems regarding the adhesiveness between the substrate and the polymer layer or the polymer layer and the gas barrier layer, flexibility and resistivity to environment on the occasion of storage under severe conditions for long time since the layer is constituted by alternatively pilling the polymer layer and the gas barrier layer each having uniform composition. Therefore, a rapid improvement is desired.
Patent Document 1Examined Japanese PatentPublication No. 53-12953Patent Document 2Japanese Patent PublicationOpen to Public Inspection(hereafter referred to as JP-A)No. 58-217344Patent Document 3WO 00/026973Patent Document 4JP-A No. 2004-9395